1. Field of the Invention
This invention generally relates to a bicycle rear derailleur. More specifically, the present invention relates to a bicycle rear derailleur having a tension plate that supports a chain tensioning pulley and a guide plate that supports a chain guiding pulley where the guide plate and tension plate are mounted to a pivot shaft with independent pivotal movement with respect to one another.
2. Background Information
Bicycling is becoming an increasingly more popular form of recreation as well as a means of transportation. Moreover, bicycling has become a very popular competitive sport for both amateurs and professionals. Whether the bicycle is used for recreation, transportation or competition, the bicycle industry is constantly improving the various components of the bicycle. One component that has been extensively redesigned is the bicycle rear derailleur.
Rear derailleurs are well known and typically include a linkage structure that includes a moveable member. The moveable member is selectively manipulated in a conventional manner to position a guiding pulley to guide a chain between a plurality of gears in a gear sprocket set.
An optimal shifting condition preferably includes positioning the guiding pulley at equal distances from each of the gears in the gear sprocket set for each gear setting position of the derailleur. Specifically, with the chain around a first gear, the guiding pulley is a first distance away from the first gear. With the chain around a second gear, the guiding pulley is a second distance away from the first gear. With the chain around a third gear, the guiding pulley is a third distance away from the first gear. In optimal shifting conditions, the first, second and third distances are equal or close to being equal.
Unfortunately, the geometry of gear derailleurs and gear sprocket sets is such that the first, second and third distances are not equal and may differ undesirably. Therefore, optimal shifting conditions are not being achieved.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved rear derailleur that can achieve more optimal shifting conditions. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.